This invention relates to a cooling and lubricating fluid for metal cutting and grinding and other machining processes, particularly for industrial, heavy duty metal cutting and machining processes where the cooling and lubricating fluid is recycled and used over long periods of time.
During various metal working or machining processes such as cutting, surface grinding, tapping, milling, drilling and so forth, it is necessary to employ a cooling and lubricating fluid to reduce wear and minimize the generation of heat between the cutting tool and the workpiece thereby increasing the useful life of tools. It is also desirable to employ a fluid which is economical, can be recycled for long term reuse, and serves a protective function to inhibit corrosion of the workpiece and tool. Still further, it is desirable to employ a fluid which enables the production of workpieces having a smooth surface finish without stain or rust.
Various metal working lubricant fluids are known and are disclosed, for example, in the following U.S. patents. U.S. Pat. No. 2,825,693, Mar. 4, 1958 to Beaubien et al discloses an aqueous metal working lubricant comprising certain block coploymers in conjunction with corrosion inhibitors, anti-wear agents, and optionally, anti-foaming agents, coupling agents, germicidal agents, and so forth. U.S. Pat. No. 3,719,598, Mar. 6, 1973 to King discloses an aqueous cutting fluid containing the reaction product of boric acid with an aliphatic amine, together with a petroleum sulfonate of an amine or an alkyl metal, in combination with a nonionic wetting agent. The King patent further discloses that other ingredients may be used such as a reaction product of an amine and a fatty acid or sulfurized fatty acid, alkyl metal nitrite, silicone antifoaming agents, bactericides, and metal deactivators such as sodium mercaptobenzothiazole. U.S. Pats. No. 3,556,994, Jan. 19, 1971 and 3,992,306, Nov. 16, 1976 both to Diery et al disclose metal working and corrosion protection agents in the form of salts of aromatic sulfonamidocarboxylic acids and bissulfonamidocarboxylic acids respectively.
Additional corrosion inhibiting agents are also disclosed in U.S. Pat. No. 2,147,409, Feb. 14, 1939 to Lamprey, which discloses soluble salts of tungstic, silicic, and molybdic acids as corrosion inhibitors in antifreeze liquids which can also contain other known corrosion inhibitors such as triethylamine or sodium hydroxide. And U.S. Pat. No. 2,194,491, Mar. 26, 1940 to Bird et al, discloses the addition of mercaptobenzothiazole or its salts and soluble phosphites or hypophosphites to aqueous solutions for the purpose of decreasing the corrosive action of such solutions in cooling systems of internal combustion engines.
It is an object of the present invention to provide an improved cooling and lubricating fluid for industrial metal cutting and fabricating processes. Such processes require a fluid having low foaming characteristics, good resistance to rancidity as the fluid is recycled and reused over an extended period of time, nonstaining characteristics so that tools and workpieces are not blemished, and good hard water tolerance in order to be used with local water which may contain a considerable amount of mineral components. Of course, a satisfactory cooling and lubricating fluid must accomplish its primary purposes of cooling and lubricating. In addition, it is of great importance that the cooling and lubricating fluid minimize use of known toxic and irritating chemicals. In particular, it is highly desirable that the fluid avoid use of known or highly suspect carcinogenic chemicals. Recently sodium nitrite, which is commonly used in a variety of compositions including metal machining fluids, has become suspect as a potential carcinogenic chemical. Accordingly, it is one object of the present invention to provide a cooling and lubricating fluid for metal cutting and other machining processes without sodium nitrite. It is another object of the present invention to provide a fluid composition having excellent anti-corrosion characteristics with respect to both ferrous and nonferrous metal workpieces and tools. Still another object of the present invention is to provide a fluid composition capable of providing lubricant properties even under extreme pressure conditions and which has resistance to rancidity, foaming, hard water, and staining. These and other objects will be apparent from the following disclosure. All percentages and parts herein are percentages or parts by weight unless otherwise indicated.